Lifting jack



Feb. 18 1958 C. W. TERRY LIFTING JACK Filed Dec. 18, 1956 ATTORNEY United States Patent 2,823,958 LIFTING JACK Claude W. Terry, Post, Tex. Application December 18, 1956, Serial No. 629,017 2 Claims. (Cl. 304-29) This invention pertains to lifting jacks and more particularly to a fast acting jack for relatively high distances.

One of the particular uses envisioned for a jack in accordance with this invention is in the building construction trade. Gypsum wall board (sometimes called sheet rock) has become a popular building material. The typical individual unit comprises a board of six feet by three feet, one-half or three-quarters inch thick. As the board is somewhat heavy, diificulty is experienced in attaching a board to over head supports to form the ceilmg of a room. The task is usually performed by two men on scaffolds, each man using one hand or his head to hold the board in place while he nails it.

An object of the invention is to provide a jack for lifting and holding wall board to overhead supports while ceiling a room.

Another object is to provide a fast acting jack that provides more lifting force as the load increases in height.

A further object is to provide a jack that inherently has a wide base and therefore is stable at all times.

Still further objects are to achieve the above with a device that is sturdy, staple and reliable, yet cheap and easy to manufacture.

The specific nature of the invention as well as other objects, uses, and advantages 'will clearly appear from the following description and from the accompanying drawing, in which:

Fig. l is a perspective View of a jack in accordance with this invention in the lowered position.

2 is a side view of the jack in the raised position.

Fig. 3 is a top cross-section view taken on line 3-3 of Fig. 1.

As seen in the drawing the jack has a lift element 10. A step jack has been illustrated for simplicity. However, this element could be any of several conventional types, such as hydraulic or a winch and cable system. It has a barrel or sleeve 12 in which stem 14 is mounted for translational movement. This translational movement is controlled by lever 16. When lever 16 is oscillated up and down with control 17 in one position, this forces stem 14 upward in barrel 12. When lever 16 is oscillated with control 17 in a second position, this permits gravity to lower stem 14. In short, there is a sleeve 12, stem 14, and means for forcing the stem upward in the sleeve.

Three legs 18 are pivoted to the barrel 12 at points 20. Three braces 22 are pivoted to the lower end of stem 14 at points 24. The legs 18 are pivoted at points 26 to a caster roller 30 through foot 32. Braces 22 are also pivoted to foot 32 at .points 28. As seen in the drawings, the legs are longer than the braces.

'When stem 14 is forced upward in the barrel, the points 24 approach points 20. This changes the triangles which have the angles at 20, 24, and 26, so that the angle at 24 becomes larger and the angles at 20 and 26 become smaller. The resulting motion is that point 20 is moved upward. Therefore, the total motion of point 24 is the sum of movement of stem 14 relative to barrel 12 and the movement of barrel 20 relative to the support of casters 30 (not shown).

The first movement described, that of the stem and 2,823,958 Patented Feb. 18, 1958 barrel, will be the same for every oscillation of lever 16 regardless of the height of stem 14. However, the second movement, that of the barrel relative to a floor, will vary according to the height of the stem. It will be evident from a study of the drawing that the second movement will be less for each oscillation of the lever as the height of the stern increases. Therefore, as the height of the stem increases, the same force on lever 16 will result in greater force of stem 14 upon the load (not shown). The law of motion which the stem follows will depend upon the particular design of the jack; that is, the length of legs 18; the length of braces 22; the position, both vertical and horizontal, of points 20 on barrel 12; the position, both vertical and horizontal, of points 24 on stem 14; and the position of points 26 and 28 on foot 32. Any or all of these design factors could be made adjustable for a single jack. For exam ple, the legs 18 could be made adjustable as to length and different connections provided on the barrel for point 20.

For use in lifting wall board as mentioned in the introduction, a plate 34 is attached by collar 36 to top of stem 14. With the stern in the lower position as illustrated in Fig. l a piece of wall board is placed upon the plate and then the lever manipulated. At first the movement is quite rapid, and the force exerted by the plate 34 upon the wall board relatively small. As the board approaches and touches the overhead supports (not shown) the movement is slower and the force with which the board is pressed against the supports is greater. The board can then be nailed in place by one man.

Another contemplated use is as an aircraft jack. Any convenient terminal piece could be used in lieu of plate 34. As the jack first begins to lift the load, the rate at which the stem moves is relatively great. However, as the load is lifted higher the possible force increases, while the rate of movement decreases.

It will be apparent that the embodiment shown is only exemplary and that various modifications can be made in construction, materials, and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

1. A lifting device comprising; a sleeve, a stem adjustably mounted in said sleeve and including a plate transversely mounted thereon, mechanical means for moving the stem relative to the sleeve, a plurality of legs each pivotally connected at their upper ends to said sleeve at a base of the parametral surface thereof, braces pivotally connected at one end thereof to said stem at the lower portion thereof, said braces being of a length which is only slightly less than the length of said legs, and connecting means connecting the lower end of said legs with the other ends of said braces whereby upon actuation of said mechanical means said lifting device may be raised a distance which is substantially equal to the length of said braces.

2. A lifting device as in claim 1 wherein said connecting means comprise feet to which are individually pivoted the lower ends of said legs and the other ends of said braces whereby upon extension of said stem in said sleeve said legs and said braces will he folded into substantially coaxial relationship relative to said stern.

References Cited in the file of this patent UNITED STATES PATENTS 1,064,798 Walte lune 17, 1913 1,685,144 Austin Sept. 25, 1928 1,735,992 Bode Nov. 19, 1929 2,031,097 Bucky Feb. 18, 1936 2,260,993 Johnston Oct. 28, 1941 2,499,005 Sellers Feb. 28, 1950 2,588,399 McQuin Mar. 11, 1952 

